Device for detecting double sheet films

Abstract

On a suction device (4, 5, 6, 21) for separating sheet films (3a) from a sheet-film stack (3), a thickness sensor (10, 11, 15, 17, 19) is mounted so as to be pivotable together with said suction device. The suction device (6, 21) releases the sheet film (3a) to be removed from a sheet-film stack (3) by bending its front section. The thickness sensor (10, 11, 15, 17) which has a forklike design is spring-biased to move onto the bent area of the sheet film (3a) still located on sheet-film stack (3). The thickness sensor comprises two levers (10, 11) with rollers (15, 17), one lever (11) being pivotable relative to the other lever (10). Depending on its path of pivotal movement the pivotably mounted lever (11) actuates a switch (19). If there is more than one sheet film (3a) between the rollers (15, 17) of the levers (10, 11) switch (19) is actuated which interrupts the sheet-film removal operation and causes its repetition. Even if the removal operation must be repeated several times the sheet film (3a) to be removed remains on the sheet-film stack (3), which prevents it from being subjected to any undesired wear and tear.

We claim: 
     
       1. A device for detecting double sheets in an apparatus for separating a sheet film from a sheet-film stack, preferably a stack contained in a supply magazine, having a suction device which separates the sheet film to be removed by bending a front area of the film which is engaged by the suction device, with respect to the sheet film plane, and for removing the front area film from the stack, characterized in that a thickness sensor (10, 11, 15, 17, 19) is moved into the bent front area of the sheet film (3a) to a sending position while said film is still located on the sheet-film stack (3). 
     
     
       2. A device according to claim 1, characterized in that the thickness sensor comprises levers (10, 11) which enclose in a forklike manner the bent front area of the sheet film (3a). 
     
     
       3. A device according to claim 1, characterized in that the thickness sensor comprises a first and a second lever (10 and 11 respectively), the first lever (10) having one end which is pivotable about a journal (9) and another end which senses the position of upper surface of the bent front area of the sheet film 3a, the second lever (11) comprising a two-armed lever hinged to the first lever (10) so as to be pivotable about a journal (12) and the second lever (11) having a first lever arm (11a) having and end which serves the position of a lower surface of the bent front area of the sheet film 3a. 
     
     
       4. A device according to claim 3, characterized in that the second lever (11) having a second lever arm (11b) associated with a switch (19), the second lever (11) being spring-biased into contact with the first lever (10) in the sensing position associated with the bent front area of the sheet film (3a). 
     
     
       5. A device according to claim 3, characterized in that at the ends of the levers (10, 11) associated with the sensing area, rollers (15 and 17 respectively) are mounted which are associated with the upper and lower surfaces respectively of the bent front position of sheet film (3a). 
     
     
       6. A device according to claim 3, characterized in that the second lever (11) is positively guided on the first lever (10) in an area of the second lever arm (11b), which is associated with a switch (19). 
     
     
       7. A device according to claim 1, characterized in that the first lever (10) of the thickness sensor (10, 11) and the suction device (4, 5, 6, 21) are arranged so as to be pivotable about a journal (9). 
     
     
       8. A device according to claim 1, characterized in that a first and a second abutment (5b and 20 respectively) are arranged on the suction device (4, 5, 6, 21), said first and second abutments extending into a path of movement of the thickness sensor (10, 11), the first abutment (5b) being associated with the sensing position of thickness sensor (10, 11) and the second abutment (20) being associated with an initial position of thickness sensor (10, 11), the second abutment (20) being designed such that the second abutment can be moved out of the path of movement of thickness sensor (10, 11). 
     
     
       9. A device according to claim 8, characterized in that an inclined surface (10b) is molded to the first lever (10), said inclined surface being arranged obliquely to a plane of movement of said first lever and associated with second abutment 20. 
     
     
       10. A device according to claim 1, characterized in that the thickness sensor is arranged on a shiftable mounting member which is guided in parallel with the bent off front area of the sheet film (3a).